1. Field of the Invention
The present invention relates to an apparatus for detecting defects in cigarette bundles formed in layered rows in buckets attached to a bucket conveyor for transport through the inspection apparatus. The detected defects include a "tip fail state" in which the top content of a cigarette is missing, lack of the filter and a shortage in the number of cigarettes in a given row.
2. Description of Related Art
In order to examine cigarette bundles conveyed by a bucket conveyor, sensing means are necessary to sense the state of the respective layered rows of bundled cigarettes to output a defect signal. Such sensing means are disclosed in Japanese Examined Utility Model Publication No. 58-5517 by the same applicants as the present application. This publication discloses a photosensitive device consisting of light emitters provided at both sides of each layer of cigarettes lying in buckets, and light receivers, i.e. photoelectric tubes. The phototube senses defects in the cigarettes by detecting the strength of the reflected light received, and issues a defect output signal.
For example, the output signal from the photoelectric tube examining seven cigarettes in a layer of a bundle of cigarettes in a bucket is shown in charts (I) through (IV) of FIG. 5. In FIG. 5, chart (I) shows that a respective row of cigarettes are in a normal condition. In this instance, the phototube output signal remains at a constant voltage level throughout the time the row of cigarettes is examined, namely the length of time for the bucket to traverse the phototube.
Chart (II) shows a state where the tips of two cigarettes are missing. The signal issued by the photoelectric tube is shown as a rectangular pulse in accordance with the defective state of the cigarette tips.
Chart (III) shows a state wherein two cigarettes do not have filters 1b. The signal output of the photoelectric tube is shown in a manner similar as that in chart (II). However, since the filter is longer than the missing content 1a, the voltage signal shown in this chart has a higher level than that of chart (II).
Chart (IV) shows a state wherein a portion of cigarette 1 is short and where a neighboring portion is missing or out of position. Since the length of the defective portion or portions is greatest in charts (I) through (IV), the output signal is also correspondingly the highest. In the Figures, reference numeral 101 indicates a space between cigarettes.
Where a conventional sensing means is used for detecting the signal emitted from the photoelectric tube, the signals disclosed in FIG. 6 are considered. In that Figure, three layers or rows of cigarettes 1 consisting respectively of seven, six and seven cigarettes, are arranged in bucket 2b. The gate time showing the time of passage of the internal length of a cigarette row is detected as gate signals B and C. Only when a defect in a cigarette is found within the time interval shown by signals B and C, i.e. only when a defect output signal D is emitted, is final defect signal E output. The final defect output signal E is used as a signal for eliminating a defective row of cigarettes, or for stopping the bundle conveying operation as is known to those skilled in the cigarette inspection art.
In the normal state, i.e. in the absence of a detected defect, the defect output signal remains at zero volts indicated by signal F. Since no defect output signal is generated in the gate signal B or C, the final defect output signal G is retained at the zero volt level and thus no output signal is generated for eliminating a cigarette bundle, or alternatively stopping the conveyor operation.
In the circumstances illustrated in FIG. 6, it is noted that the bucket 2b has a space so that the cigarettes 1 are not damaged as they are inserted and/or conveyed. Accordingly, the cigarettes 1 in the bucket 2b are moved in a direction opposite to the direction of movement of the bucket in dependence upon the intermittent movement of the bucket 2b. Consequently, irregular spaces shown by the dotted line as signal L of FIG. 7 may occur although the bundles of cigarettes are not in a normal or acceptable state. If the spaces are detected a defective output signal, a final defective output signal would be erroneously emitted and the cigarette bundle concerned would be eliminated from the bucket by means known to those skilled in the art to which the invention pertains.